canonicalize
Canonicalize or decode the input string. Canonicalization is simply the operation of reducing a possibly encoded string down to its simplest form. This is important because attackers frequently use encoding to change their input in a way that will bypass validation filters, but still be interpreted properly by the target of the attack. Note that data encoded more than once is not something that a normal user would generate and should be regarded as an attack.
canonicalize(input, restrictMultiple, restrictMixed) → returns string
Argument Reference
input string Required
restrictMultiple boolean Required
restrictMixed boolean Required
throwOnError boolean
Default: false
false
Compatibility
ColdFusion:
BoxLang:
bx-esapi module. Examples Sample code invoking the canonicalize function
Canonicalize the simple HTML entity encoded string.
<cfoutput>#canonicalize("<",false,false)#</cfoutput>Expected Result: <
(Adobe CF 11+ example with throwOnError parameter set to true) Enforce multiple and mixed encoding detection. Mixed encoding is detected as the data is encoded using URL and HTML entity encoding. Multiple Encoding is also detected.
<cftry>
<cfoutput>#canonicalize("%26lt; %26lt; %2526lt%253B %2526lt%253B %2526lt%253B",true,true, true)#</cfoutput><br/>
<cfcatch type="any" >
<!--- throws Error when throwOnError set to true (CF11+) when mixed or multiple encoding is detected. --->
<cfdump var="#cfcatch#" >
</cfcatch>
</cftry>Expected Result: Error Message: Input validation failure. The log message will contain more detailed information on the error.
(Adobe CF 11+ example with throwOnError parameter set to false) Enforce multiple and mixed encoding detection. Mixed encoding is detected as the data is encoded using URL and HTML entity encoding. Multiple Encoding is also detected.
<!--- an Empty string will be returned if the throwOnError is set to false and multiple or mixed encoding is found --->
<cfoutput>#canonicalize("%26lt; %26lt; %2526lt%253B %2526lt%253B %2526lt%253B",true,true, false)#</cfoutput>Expected Result: [Empty string]
Enforce mixed but not multiple encoding detection returns an Empty String.
<cfoutput>#canonicalize("%25 %2526 %26##X3c;script&##x3e; &##37;3Cscript%25252525253e",false,true)#</cfoutput>
<!--- The following example is purely to show the error when using `throwOnError` parameter set to true (Adobe CF11+) --->
<cftry>
<cfoutput>#canonicalize("%25 %2526 %26##X3c;script&##x3e; &##37;3Cscript%25252525253e",false,true, true)#</cfoutput><br/>
<cfcatch type="any" >
<!--- throws Error when throwOnError set to true. --->
<cfdump var="#cfcatch#" >
</cfcatch>
</cftry>Expected Result: [Empty string]
Mixed encoding is detected as the data is encoded using URL and HTML entity encoding. Multiple Encoding is also detected.
<!--- Decodes the string using both percent and HTML Entity encodings as the flags were set to false --->
<cfoutput>#canonicalize("%26lt; %26lt; %2526lt%253B %2526lt%253B %2526lt%253B",false,false)#</cfoutput><br/>
<cfoutput>#canonicalize("&##X25;3c",false,false)#</cfoutput><br/>
<cfoutput>#canonicalize("&##x25;3c",false,false)#</cfoutput>Expected Result: < < < < < < <
http://www.planetpdf.com/codecuts/pdfs/tutorial/jsspec.pdf see section 2.7.5 for JS Encoding
<cfoutput>#canonicalize("\\U003C",false,false)#</cfoutput><br/>
<cfoutput>#canonicalize("\\X3C",false,false)#</cfoutput>Expected Result: < <
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https://cfdocs.org/canonicalize
